This invention generally relates to electroplating and electroless plating apparatus and methods.
Electroplating is a common process for depositing a thin film of metal or alloy on a substrate such as, for example, a variety of electronic components and semiconductor chips. In a typical electroplating apparatus or system, the substrate is placed in a suitable electrolyte bath containing ions of a metal to be deposited. The substrate is connected to the negative terminal of a power supply to form a cathode, and a suitable anode is connected to the positive terminal of the power supply. Electrical current flows between the anode and cathode through the electrolyte and metal is deposited on the substrate by an electrochemical reaction.
In many electronic components, it is desirable to deposit the metal film with a uniform thickness across the substrate and with uniformity of composition. However, the electroplating process is relatively complex, and various naturally occurring forces may adversely affect the electroplating process. Most significantly, the electrical current or flux path between the anode and the cathode may spread or curve, making it difficult to achieve uniform electrodeposition.
An object of this invention is to provide an improved electroplating apparatus and method.
Another object of the present invention is to selectively and controllably adjust the amount of electric flux passing towards selected areas of a workpiece, during an electroplating process, in order to deposit a metal film or alloy with a uniform thickness across the workpiece. This apparatus could also be used to regulate solution flow in an electroless plating deposition bath which would in turn make the bath more capable of depositing in small through holes.
A further object of this invention is to use a unique anode shield/material flow apparatus that can be controllably adjusted on the fly, during an electroplating process, to selectively isolate areas of the workpiece.
Another object of this invention is provide an infinitely adjustable mechanism that can selectively isolate areas to be electroplated.
These and other objectives are attained with an apparatus and method for electroplating a workpiece. The apparatus comprises, generally, an anode, a cathode, and a selective shield/material flow assembly. In use, both the anode and the cathode are immersed in a solution, and the cathode is used to support the workpiece. During an electroplating process, the anode and the cathode generate an electric field emanating from the anode towards the cathode, to generate a corresponding current to deposit an electroplating material on the workpiece.
The selective shield/material flow assembly is located between the anode and the cathode, and forms a multitude of adjustable openings. These openings have sizes that are adjustable during the electroplating process for selectively and controllably adjusting the amount of electric flux passing through the selective shield/material flow assembly and the distribution of the electroplating material on the workpiece.
With a preferred embodiment of the invention, described in detail below, the selective shield/material flow assembly is used to selectively isolate an area of the workpiece from plating by use of an individual adjustable selective shield/material flow mechanism. The selective flow material flow assembly can comprise one or more selective shield material flow mechanisms. The selective shield material flow assembly can be adjusted selectively on one, two, or multi axes. In another embodiment, the shielding, in the case of electroless plating, also slows or increases solution flow to areas of the plating surface and thus lowers or increases plating thickness and rates. The shielding or baffling also slows/isolates solution flow to the plating surface and thus lowers or raises plating thickness/rates This causes more plating uniformity in panel or pattern plating equipment.
Further benefits and advantages of the invention will become apparent from a consideration of the following detailed description, given with reference to the accompanying drawings, which specify and show preferred embodiments of the invention.